1. Field of the Invention
The invention lies in the field of monitoring the temperature of the mechanical members of a vehicle driven by an internal combustion engine. While the vehicle is traveling, in order to estimate the temperature of a mechanical member, generally the thermal energy dissipated by friction in this member is calculated, as well as the thermal energy given up by this member to the surrounding environment, i.e. to the air flowing under the engine cowling or under the vehicle. In the case of four-wheel drive vehicles, it is, for example, necessary to know the temperature of the coupler which transmits the available engine torque from one set of wheels of the vehicle to the other set of wheels of the vehicle.
2. Description of Related Art
Patent application EP 1 308 336 describes a method of managing a coupler according to the heating of the coupler. However, this document provides for assessing the heating of the coupler, either in terms of temperature difference with respect to an initial state, or in terms of thermal energy produced by friction. This document does not therefore provide a method for calculating the absolute temperature of the coupler. This temperature can be a crucial parameter, if, for example, the outside temperature is itself high, or if the coupler is already hot without this being taken into account by the system, following a start-up of the vehicle after a not very prolonged stop has not allowed the coupler to cool to the ambient temperature. For reducing the manufacturing costs and maintenance costs of the vehicle, the number of temperature sensors installed on the vehicle is limited to the minimum necessary. The monitoring methods developed should therefore preferably be able to forego having a temperature sensor on the member to be monitored (e.g. a coupler).
Incidentally, the monitoring methods developed will use, or preferably will not use a temperature sensor for the air outside the vehicle. Finally, for saving manufacturing costs and energy consumed by the vehicle, all the control electronics of the vehicle should be able to be switched off when the vehicle is at a prolonged stop. Thus solutions are sought that avoid maintaining an electronic clock on standby linked to the control system present. The moment the electronic control systems of the vehicle are powered up, they must therefore be capable of defining an initial value of temperature of the members from which they subsequently calculate the temperature variations by performing heat balances.
Using an arbitrary default value is risky since if the vehicle restarts after a short stoppage period, this default value risks being underestimated. There is a risk therefore of underestimating all the subsequently calculated temperatures of the coupler or of the member and damaging the member to be monitored.